/Engine/Plugins/2D/Paper2D/Source/Paper2D/Classes/SpriteEditorOnlyTypes.h
Takes all polygon shapes and generates a list of triangles from them. Output will contain a multiple of 3 points, each set is one triangle. Always ignores circles, but can include or ignore boxes based on bIncludeBoxes.
void Triangulate ( [TArray](API\Runtime\Core\Containers\TArray)< FVector2D > & Target, bool bIncludeBoxes ) const